This article is from the Ergonomics and Typing Injury FAQ, by Dan Wallach firstname.lastname@example.org with numerous contributions by others.
Mac (System 6.0.4), Windows
Provides calendar, keyboard watch, email watch, and system information.
Warns when to take a break (configurable). Has a few recommendations on
posture, and exercises. Sound-oriented, will probably work best with sound
card (PC) or with microphone (Mac). Should be possible to record your own
messages to warn of break.